This is the essential message that needs to be conveyed to the public, and what I mean when I say “climate change is simple.” There are all sorts of interesting debates to be had about how best to proceed, what policies are most effective, what level of warming is tolerable … all that stuff is complicated and in need of democratic deliberation. But from the public’s point of view, the core fact here is that we have to do something or we’re screwed . Sitting this out is not an option, at least not a sane one.